Rock bolt assembly for upgrouting operations



April 23, w68 c. WlLLlAMS 3,379,019

ROCK BOLT ASSEMBLY FOR UP-GROUTING OPERATIONS Filed May 5, 1965 3 Sheets-Sheet l /NVE/vro@ CHESTER Z W/LL/AMS B ifm- April 23, 1968 c. l. WILLIAMS 3,379,019

ROCK BOLT ASSEMBLY FOR UP-GROU'I-'ING OPERATIONS Filed May 5, 1965 5 Sheets-Sheet. 2

April 23, l9698 c. WILLIAMS 3,379,019

-GROUTLNG OPERATIONS ROCK BOLT ASSEMBLY -FOR UP Filed May 5, 1965 5 Sheets-Sheet 3 United States Patent O 3,379,019 ROCK BOLT ASSEMBLY FR Ul- GROUTING OPERATIONS Chester I. Williams, 347 Greenhriar SE., Grand Rapids, Mich. 495536 Filed May 3, 1965, Ser. No. 452,592 6 Claims. (Cl. 61-45) ABSTRACT F THE DISCLOSURE A plug for engagement with a rock bolt rod to isolate a portion of a hole occupied by the bolt from an injected charge of grout, the plug having a passage for receiving a tube alongside the rod.

This invention relates to the construction of rock bolts. It is common practice to grout a rock bolt in the installed condition by filling the hole in the rock formation around the rock bolt with an initially liquid cementitious composition known as groutf This material is pumped into the hole under pressure, and flows into the interstices and irregularities in the wall of the hole, and bonds to the bolt as the cement sets. The result is a protective covering for the bolt, and an effective means of transferring stress from the bolt over to the rock formation.

When the hole in which the bolt is installed extends downward from the surface, the full grouting of the rock bolt in one operation presents relatively minor problems. When the hole runs at an upward inclination, however, a problem is encountered in preventing back-flow of the liquid grout, and confining the grout to the area where it is wanted under pressure. A second problem is present with regards to properly venting the air from the hole as the grout is injected under these conditions. It may also be desirable to initially grout exclusively the inner end of a rock bolt in any inclination, as in cases where softness of the rock formation prevents a sufficient set of a mechanical anchor to permit pre-stressing the bolt. In all these partial grouting operations, it has rarely been possible to generate sufficient grout pressure and venting action to properly place the fluid material.

This invention makes possible the selective grouting of a portion of the length of the rock bolt assembly, regardless of the direction of inclination of the hole. It also becomes possible to isolate a portion of the hole from which grout is to be excluded. The latter arrangement is valuable where the roei; bolt hole traverses a fault in the rock formation which would otherwise absorb vast quantities of grout without any valuable effect. The isolation of portions of the hole is accomplished by the use of plugs traversed by the rock bolt and by vent tubes, the preferred form of the invention having plugs which are rotatable on the bolt rods so that mechanical anchor devices which are set rotatably may be actuated by rotation of the bolt rod from the surface without damaging the vent tubes.

The features of the invention will be analyzed in detail through a discussion of the particular embodiments illustrated in the drawings. In the drawings:

FIGURE 1 shows a rock bolt assembly embodying one form of the invention installed in a hole in the rock formation, prior to grouting.

FIGURE 2 illustrates a modified form of the invention installed in a hole in the rock formation, prior to grouting.

FIGURE 3 illustrates a further modification of the invention installed in a hole in a rock formation, prior to grouting.

FIGURE 4 is a section on the plane 4 4 of FIG- URE 3.

Patented Apr. 23, 1968 rice FIGURE 5 is a section of the plane 5 5 of FIG- URE 2.

FIGURE 6 is a section on an enlarged scale of the plane 6 6 of FIGURE 2.

FIGURE 7 is a section on the plane 7 7 of FIG- URE 6.

FIGURE 8 shows a further modification of the invention installed in a hole in a rock formation.

FIGURE 9 is a section on the plane 9 9 of FIG- URE 8.

FIGURE 10 is a section on the plane 1li-10 of FIG- URE 8.

FIGURE 11 is a section on the plane 11 11 of FIG- URE S.

FIGURE 12 is a section on an axial plane showing the conformation of a rubber plug prior to installation.

Referring to FIGURE 1, the rock bolt assembly generally indicated at 20 is shown installed in a hole 21 in a rock formation 22. The assembly includes the rod sections 23-26 interconnected by the couplings 27-29. The outer extremity of the rod section 23 is threaded as shown at 3i), and is engaged by a nut 31 bearing against a washer 32 resting on the bearing plate 33 supported by the surface 34 of the roclr formation. The vent tube 35 traverses a suitable opening in the plate 33, and extends along the length of the rock bolt assembly through the passage 36 in the rubber plug 37. This plug is shown in section in FIGURE 12, and is initially conical on its peripheral surface. The purpose of this plug is to seal off the inner portion 21a of the hole 2l in the rock formation, and the insertion of the rock bolt assembly with the plug in position is facilitated by forming the outer portion 2lb of the hole in a somewhat larger diameter. The thrust involved in inserting the plug, and in resisting the pressure of the grout, is transferred to the end of the coupling 21 through one or more slip rings 38.

The plug 37 is rotatably mounted on the rod section 26 in order to permit a rotation of the bolt rod to set the anchor device generally indicated at 39. The plug 37 is positioned axially along the bolt rod by the presence of the end of the coupling 29, which functions as an abutment. When the anchor device has been set, the portion of the hole inwardly from the plug 37 may be grouted by injection of grout through the tube 35, with the air confined in the hole being vented outward through the central bore 4h of the rod sections. In soft rock formations, for the setting of the anchor device still does not provide sufficient retention to permit developing the full tensile strength of the bolt rod, the hardening of the injection of grout will supplement the effect of the anchor to provide the necessary resistance for a full pre-stressing of the rock bolt assembly. This is done by tightening the nut 32.

After the pre-stressing has been completed, it may be desirable to grout the portion 211') of the hole, and this may be accomplished by pulling the tube 35 axially to the left out of the plug 37. This should be done shortly after the initial charge of grout has been injected in the portion Zia of the hole so that the tube 35 may be purged. When the tube 35 has been cleared, it is then free to function as a Vent tube so that grout can be injected through the short tube 4I to occupy the portion 2lb of the hole. When thus installed, the entire bolt assembly is provided with a protective covering, and also a means for transferring stresses directly from the bolt over to the rock formation. Where the periphery of the bolt rod sections is corrugated, or otherwise deformed to increase the bond to the grout, it is preferable that the portion of the rod occupied by the plug 37 be machined to a cylindrical surface so that the plug will rotate more freely with respect to the bolt rod, and will also preserve a better seal. Where it is desirable to grout the portion 2lb of the hole, the sealing of the hole at the outer extremity is normally accomplished by the provision of a quantity of sealing mastic packed into the entrance of the hole as shown at 42, or a plug similar to the plug 37 may be installed in this position.

Referring to FIGURE 2, the rock bolt assembly generally indicated at 43 is installed in a hole 44 in the rock formation 45. In this particular installation, the hole 44 is of essentially the same diameter throughout its length. The assembly shown in FIGURE 2 also includes a bearing plate 46 (shown on enlarged scale in FIGURE 5), a bearing washer 47, and a nut 48 engagingly threaded outer extremity 49 of the bolt rod. In this modiiication of the invention, the bolt rod is also composed of a series of sections 50-51 interconnected by couplings 52. The coupling S3 interconnects the straight rod sections Si) and 51 with the solid anchor rod 54 crimped into a wave-like conformation, which is connected at its inner extremity to the expandable anchor device 55. The anchor devices shown in FIGURE 1 and FIGURE 2 include an expandable shell 56 which is discontinuous along one side to produce a C-shaped configuration in cross section, and has a conical inside surface engaged by the similar peripheral conical service on the expander 57. This expander is in threaded engagement with the outer extremity of the rod 54, and rotation of the rod will cause the expander (due to frictional rotative drag on the wall or the rock formation) to move axially to the left and expand the shell 56 into soiid engagement with the rock formation. Where the rock formation is somewhat soft, the engagement of the anchor is supplemented by the engagement of the crimped rod S4 wtih the grout that can be injected in the hole at a position inwardly from the plug S8. To provide a preliminary retention of the rock bolt assembly within the hole during the installation procedure, the resilient ring 59 is incorporated as shown. Grout pressure effective on the plug 58 will be resisted by the action of the resilient fingers of the ring 59 engaging the wall of the hole 44 on an incline which extends to increased circumscribed diameter toward the outer portion of the rock bolt assembly The injection of the grout into the area inwardly from the plug 58 requires the presence of a vent tube 60 extending to the anterior portion of the hole, and a supply tube 61 extending preferably just through the plug 53. The injection of grout in the supply tube is accompanied by withdrawal of air through the vent tube, with a net result that the portion of the rock bolt assembly inward from the plug 5S can be thoroughly grouted. The outer extremity of the assembly, after pre-stressing of the bolt, can also be grouted (if desired) by the procedure outlined in connection with FIGURE l. The presence of the tubes 60 and 61 is accommodated by the plate 46 at the keyhole-shaped opening, in which the major portion 62 is of a size to receive the rod 50, with a lateral extension 63 being proportioned to receive the tubes 60 and 61 without interference from the washer 47 or the nut 4S.

Referring to FIGURE 3, the rock bolt assembly illustrated in this View includes a series of solid rod sections 6'-66 and the undulated solid anchor rod 67 interconnected by the couplings 68-70. The surface plate 71 is similar to that shown in FIGURE 5, and the washer 72 and nut 73 transfer stresses from the plate to the threaded portion 74 of the outer rod section 6a. The vent tube 75 extends preferably over the full length of the rock bolt assembly, and the supply tube '76 traverse the rubber plug 77 in the manner discussed in connection with FIGURE 2. The forced insertion of the initially conical plug 77 will have a tendency to distort it into the form illustrated in FIGURE 3. rl`he purpose of the plug is to seal off the inner portion of the hole 78 in the rock formation 79 so that the portion of the hole surrounding the undulated anchor rods 67 may be solidly grouted. After the grout has hardened, the retention of the undulated rod 67 will permit the anchor assembly to be pre-stressed by application of torsion to the nut 73. A retaining ring Sil is preferably incorporated as discussed in the connection with i the ring 59 shown in FIGURE 2. A C-shaped ring 81 may be incorporated with either a relatively tight tit around the rod 67, or in threaded engagement. This ring increases the support for the iexible retainer 80, and the peripheral discontinuity of the ring accommodates the tubes 75 and '76.

Referring to FIGURE 8, the rock bolt assembly illustrated in this view includes a group of rod sections as shown at 82 and 83 which are provided with surface irregular-ities to increase the bond to the surrounding grout. The connecting rod section 84 is threaded over a portion of its length, and all of these rod sections are tubular to permit the interior bore to be utilized as a vent passage. These rod sections are interconnected by the couplings S5 and 86. The portions of the rod sections occupied by the rubber plugs 87 and 88 are peripherally machined into cylindrical configuration to 4facilitate rotation of the rod assembly with respect to the plugs so that the tubes @-96 will not be rotated with respect to the rock formation during the rotated setting of the anchor device 91. Slip rings may be incorporated as shown at 92 and 93 to minimize the torsional effect of the friction between the ends of the couplings and the rubber plugs as the rod assembly is rotated.

The assembly shown in FIGURE 8 is primarily intended to isolate the portion of the hole 94 in the rock formation adjacent the fault 95 which would otherwise assume indefinite quantities of grout pumped into the hole under pressure. The tube 99 traverses both the plugs 87 and Sti, and becomes the passage for supplying grout to the portion of the hole 96 inward from the plug 83. When this operation has been completed (after the setting of the anchor device 91 the position of the hole betwen the plug 87 and the surface plug 97 can be grouted by supplying grout through the tube 9S, and venting the air in this area through the tube 89 terminating just outward from the plug 87. The bearing plate 99 is similar to the plate shown in FIGURE 5, with the lateral opening enlarged a sufficient degree to accommodate the three tubes rather than the two tubes shown in FIGURE 5. The final installation of the assembly shown in FIGURE 8 will position grout in the areas shown at 16) and 101, leaving the central portion of the rock bolt assembly free of grout. Under some conditions, a length of the serrated rod shown in FIGURE 8 can itself function as an anchor device.

The particular embodiments of the present invention Vwhich have been illustrated and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention `disclosed herein, except as I am limited by the prior art.

I claim:

1. A rock bolt assembly, comprising:

a bolt rod;

an anchor device secured to said bolt rod, said anchor device being expandable by rotation of said bolt rod;

a plug Iof resiliently deformable material rotatably mounted on said bolt rod outward from said anchor device, said plug having at least one passage at the side of said bolt rod;

abutment means on said bolt rod operative to axially position said plug on said bolt rod intermediate the ends thereof;

tube means traversing said passage; and

securing means engaging the outer portion of said bolt rod for transferring forces from said bolt rod to the surface of a rock formation, said securing means including a bearing plate traversed by said tube means, said plug being remote from said bearing plate along said bolt rod.

2. A rock bolt assembly comprising:

a bolt rod;

an anchor device secured to said bolt rod;

a plug of resiliently deformable material mounted on said bolt rod outward from said anchor device, said asf/asia plug having at least one passage at the side of said bolt rod;

'abutment means on said bolt 4rod operative to axially position said plug on said bolt rod intermediate the ends thereof;

tube means traversing said passage;

securing means engaging the outer portion of said bolt rod for transferring forces from said bolt rod to the surface of a rock formation, said securing means including a bearing plate traversed by said tube means, said plug being remote from said bearing plate along said bolt rod; and

a retaining device inhibiting withdrawal of said assembly from a hole in which it is inserted, said retain- `ing device including resilient lingers disposed to engage a surrounding wall of a hole at an angle extending to an increased circurnscribed diameter outwardly along said bolt rod.

3. A rock bolt assembly, comprising:

a bolt rod;

an anchor device secured to said bolt rod;

a Iplurality of axially spaced plugs of resiliently deformable material mounted on said bolt rod outward from said anchor device, said plugs each having at least one passage at the side of said bolt rod;

tube means traversing certain of said passages in each of said plugs; and

securing means engaging the outer portion of said bolt rod for transferring forces from said bolt rod to the surface of a rock formation, said securing means including a bearing plate traversed by said tube means.

4. An assembly as defined in claim 3, wherein said anchor device is secured to the inner extremity of said bolt rod.

5. An assembly as dened in claim 3, wherein said plugs are rotatable on said bolt rod, and said anchor device is expandable and actuated lby rotation of said bolt rod.

6. An assembly as defined in claim 3 incorporating a retaining device inhibiting withdrawal of said assembly vfrom hole in which it is inserted, said retaining device including resilient fingers disposed to engage a surrounding wall of a hole at an angle extending to an increased circumscribed diameter outwardly along said bolt rod.

References Cited UNITED STATES PATENTS 3,306,051 2/1967 Howlett 61-45 2,570,003 10/1951 Palmer 61-45 2,829,502 4/1958 Dempsey 61-45 FOREIGN PATENTS 84,937 1955 Norway. 84,938 1955 Norway.

JACOB SHAPIRO, Primary Examiner. 

